Indeed, since the Iraqi regime collapsed, Syria has been getting far more attention from the Bush administration than either Iran or North Korea, the remaining members of what the president has called an "axis of evil."

In a sign that Syria may be assigned to that club, President Bush charged Sunday that Syria has developed chemical weapons. "We're serious about stopping weapons of mass destruction," he told reporters at the White House after returning from Camp David.

On Friday, he had warned Damascus that the United States was expecting "full cooperation."

"We strongly urge them not to allow for Baath Party members or Saddam's families or generals on the run to seek safe haven and find safe haven there," he said after visiting injured service members.

If the U.S. discovers that Syria is harboring such individuals, that could be the last straw, administration officials indicated Sunday.

"The Syrian government needs to cooperate with the United States and our coalition partners," Bush said Sunday.

Defense Secretary Donald H. Rumsfeld charged that top officials have either fled to or through Syria to other countries.

And Army Gen. Tommy Franks, the U.S. war commander, said Syrians make up the largest share of foreigners who are still fighting coalition forces in Iraq. "They have come in as mercenaries. They have been paid by the Iraqis. We have seen recruiting material," Franks said on CNN's "Late Edition." "And they're employed as everything from suicide bombers to small group hit squads."

Unless Damascus begins cooperating on these and other issues, Washington may take punitive measures, U.S. officials said, although military action was not specifically mentioned. After the swift Iraq operation, the public's mood may tolerate some sort of action against Syria. Already, the proposed Syrian Accountability Act, introduced last week in the House of Representatives, has strong bipartisan support.

"It's been a campaign of misinformation and disinformation about Syria since even before the war started," Imad Moustapha, Syria's deputy ambassador to Washington, said Sunday on NBC's "Meet the Press."

Syria would "warmly" welcome "the most rigid inspection regime" on weapons of mass destruction, he said, as long as it applies equally to all Middle East countries -- a veiled reference to the widespread belief that Israel possesses nuclear weapons.

Behind the scenes, Washington has also put Damascus on notice that it expects an immediate and full accounting of contraband that it says flowed into Iraq as part of an estimated $6-million worth of daily illegal trade across the Syria-Iraq border.

The administration is particularly interested in millions of dollars in dual-use equipment it says crossed from Syria into Iraq that may have helped Baghdad develop its weapons programs, according to U.S. officials

"All eyes are on Syria, and its next steps are critical. We're watching very closely to see how Syria responds to information we have confronted the government with," said a senior administration official.

Syria has quietly become a subtext of the U.S. confrontation with Iraq for at least two years, as U.S. intelligence has tracked growing trade in both directions that U.S. officials say violated U.N. sanctions against Iraq.

Despite historic animosity between rival branches of the Baath Party that have ruled both countries for decades, the Assad regime reopened a pipeline in November 2000 for 70,000 barrels of Iraqi oil to flow into Syria daily for export, U.S. officials say.

In addition, Damascus allowed Baghdad to truck as much as 140,000 barrels of oil across the border daily. The trade of the smuggled oil -- outside the U.N.'s permitted "oil for food" program for Iraq -- reportedly garnered Baghdad as much as $2 million a day.

Secretary of State Colin L. Powell met with Assad in early 2001 and came away with a promise that Damascus would stop the illicit trade. But trade soon resumed, officials say.

Other top U.S. officials and U.S. Ambassador Theodore H. Khattouf continued to pressure Damascus. But again, the Assad regime refused to heed the U.S. or entreaties from the United Nations, according to U.S. officials.

In exchange for Iraqi oil, Syrian middlemen increasingly became conduits for forbidden goods, including materiel for arms programs, the sources said.

The two-way illegal commerce, often in kind rather than in cash, started as a trickle but spiked to "astronomical levels," said the senior administration official. "It became so egregious," he said.